Thermostat or receiver enclosure vibrates or hums when heating is on.

Safety first: Turn off power before adjusting the receiver or thermostat mounting.

Steps to check:

• Tighten fixings: Ensure all mounting screws are snug but not over-tightened.
• Add damping: Fit rubber or foam pads between the receiver and the mounting surface to reduce vibration transmission.
• Relieve cable strain: Ensure cables are not pulling the unit out of alignment or causing it to vibrate against the wall.

Resolution: If humming persists and is loud, the internal transformer or relay may be faulty. Replace the receiver.